After you have uninstalled WS, go into the registry and remove Accpac from Current User & Local Machine (this will be in WOW64....)

This has worked for me in the past.  V2018 is supposed to do regacc, but do it manually just in case !!!

Then try install as Admin again.

After you have uninstalled WS, go into the registry and remove Accpac from Current User & Local Machine (this will be in WOW64....)

This has worked for me in the past.  V2018 is supposed to do regacc, but do it manually just in case !!!

Then try install as Admin again.

We tried but same issue. So I check in more detail in that PC and apparently Netframework was there (as I found a folder where expected) but was not active, so I select it from Control Panel, download and install some files and voila!!! We tried install Sage 300 2018 workstation again and no error registing .dll. And then we run preview reports without any problems. Thanks to everyone.

The older versions of Sage 300 require the old versions of .net framework to work with Crystal Report.  If your computer is a new built of Windows 10, it needs to have the old .net framework installed.  You can confirm this by going to C:\Windows\Microsoft.NET\Framework\   You would see v4.0.30319 folder only.  No need to uninstall Sage 300 and reinstall again.  Just do the following.

1.  Install old version of .net framework.  The general procedures are explained here:  https://www.groovypost.com/howto/enable-net-framework-2-windows-8/   It is quicker to invoke Windows Search, then type "appwiz.cpl" and press <Enter>.  The Programs and Features window will come up.  Click Turn Windows Features On or Off at upper left panel.

2.  Register a4wcrinterop.dll assembly.  The procedures are explained here at the third step:  https://www.tandemtechnologiesllc.com/blog/sage/sage-300/problem-registering-assembly-a4wcrinterop-dll-installation/